Zilpaterol is a known adrenergic β-2 agonist having the following structure:

The IUPAC name for zilpaterol is 4,5,6,7-tetrahydro-7-hydroxy-6-(isopropylamino) imidazo[4,5,1-jk]-[1]benzazepin-2(1H)-one. The Chemical Abstracts name for zilpaterol is 4,5,6,7-tetrahydro-7-hydroxy-6-[(1-methyl-ethyl)amino]-imidazo[4,5,1-jk][1]benzazepin-2(1H)-one.
The generic structure encompassing zilpaterol has two chiral atoms:

Consequently, zilpaterol has four stereoisomers. These stereoisomers may be identified as “(6R,7R),” “(6R,7S),” “(6S,7R),” and “(6S,7S).” Racemic trans zilpaterol (i.e., a mixture of the (6R,7R) and (6S,7S) stereoisomers) has been identified in the literature as “RU42173.” These trans stereoisomers have the following structures:

It is well known that zilpaterol, various zilpaterol derivatives, and various pharmaceutically acceptable acid addition salts of zilpaterol and its derivatives may, for example, be used to increase the rate of weight gain, improve feed efficiency (i.e., decrease the amount of feed per amount of weight gain), and/or increase carcass leanness (i.e., increase protein content in carcass soft tissue) in livestock, poultry, and/or fish. In U.S. Pat. No. 4,900,735, for example, Grandadam describes zootechnical compositions of racemic trans zilpaterol and salts thereof that may be used to increase the weight and meat quality of warm-blooded animals, including cattle, pigs, sheep, and poultry. And U.S. Pat. No. 7,207,289 describes using ionophore/macrolide/zilpaterol dosing regimens to increase beef production, reduce feed intake while maintaining beef production, and reduce incidences of liver abscess in cattle.
Methods for making zilpaterol are known in the art. For example, in U.S. Pat. No. 4,585,770, Fréchet et al. discuss compounds encompassed by a genus characterized as 6-amino-7-hydroxy-4,5,6,7-tetrahydro-imidazo[4,5,1-jk][1]-benzazepin-2[1H]-one derivatives and pharmaceutically acceptable acid addition salts thereof. The derivatives correspond in structure to the following formula:

Here, R can be various substituents, and the wavy lines indicate that the bonds to the 6-amino and 7-OH groups have the trans configuration. This genus encompasses racemic trans zilpaterol when R is isopropyl.
The methods reported in U.S. Pat. No. 4,585,770 use 4,5-dihydro-imidazo[4,5,1-jk][1]benzazepin-2,6,7[1H]-trione-6-oxime as an intermediate. This compound corresponds in structure to Formula (I):

As indicated in U.S. Pat. No. 4,585,770, 4,5-dihydro-imidazo[4,5,1-jk][1]benzazepin-2,6,7[1H]-trione-6-oxime may be formed from starting materials that have been long known in the art. U.S. Pat. No. 4,585,770 illustrates the use of two such starting materials. In both examples, the starting materials are used to form 5,6-dihydro-imidazo[4,5,1-jk][1]benzazepin-2,7-[1H,4H]-dione, which, in turn, may be used to make 4,5-dihydro-imidazo[4,5,1-jk][1]benzazepin-2,6,7[1H]-trione-6-oxime.
In one of the examples in U.S. Pat. No. 4,585,770, the starting material is 1,3-dihydro-1-(1-methylethenyl)-2H-benzimidazol-2-one, which is described in J. Chem. Soc. Perkins, p. 261 (1982):
